Vibratory screen



Dec. 3, 1963 A. K. F. FFOULKES 3,113,098

VIBRATORY SCREEN med Jan. 11, 1960 .s sheets-sheet 2 S9 l A um.

Dec. 3, 1963 A. K. F. FFouLKEs 3,113,098

VIBRATORY SCREEN Filed Jan. 11, 1960 3 Sheets-Sheet 3 INV/:wrom ARTHUR KINSLEY Frscms/zffouLksr .3y gun 414;, Y MMM? ATN/f United States Patent O 3,113,1l3 VEEBRATSRY SCREEN Arthur Kingsley Fischer tloullres, 4t) Ave. Keieg, Geneva, Switzerland Filed `ian. 11, 1960, Ser. No. 1,4% Claims priority, appiication Great Britain Ilan. 9, 1959 7 Claims. (Cl. 2ll9-22) This invention comprises improvements in or relating to vibratory screens.

Unless secured to heavy concrete foundations massive simple vibrating screens transmit objectionable vibration to neighbouring structures. Two or more screens are often partially balanced against one another with nearly equal and opposite motions in nearly the same plane, but it is usually impossible to perfect this balance. In consequence the speed and stroke of a vibrating screen are limited, particularly when used on the upper lioors of buildings.

lt is an object of the present invention to provide a vibratory screen in which the moving parts are of light weight permitting optimum speed and stroke without transmitting objectionable vibration to building structures.

lt is a further object of the invention to provide a screen which is capable of being used for conditioning material, for example tobacco, which is treated upon it.

According to one feature of the present invention a vibratory screen is characterized by the fact that the material of the screen is maintained in tension by spring anchoring means engaging the edges thereof and attached to stationary suspension points, which spring means yield so as to permit vibratory movement of the screen. In this way the weight of the vibrating part of the screen is reduced because no heavy vframe is required to keep the material of the screen properly stretched out.

Preferably the spring anchoring means are of such stiness that the natural period of vibration of the screen is equal to the speed at which it is intended to be driven. By tuning the `springs to the speed of the screen in this way, driving forces are minimised and the driving elements for causing the screen to vibrate may be reduced to the lightest construction.

Preferably the suspension comprises guide means so that the vibration takes place in such `a sense as to propel material resting on the screen sections along the surface thereof. Means may also be provided to convey a current of air through the screen during operation and such air may be used to condition material undergoing treatment on the screen. For example if Warm dry air is used the material may be dried but by regulating the moisture content of the air the material may be prevented from drying or even caused to acquire moisture; at the same time the material can be brought to any desired speciic final temperature.

ln one construction the screen is combined with a winnowing device capable of classifying delivery to the screen so that heavier material is delivered to a part of the screen `furthest from the delivery end and lighter material to a part nearer to the delivery for the purpose of ensuring that the denser material its adequately conditioned.

Diiterent parts of the screen may be caused to vibrate in dierent phase from one another, if desired, so as to balance the reciprocating forces, as required.

The following is a `description by way of example of certain constructions in accordance with the invention.

ln the accompanying drawings,

lGURE l is a longitudinal lsection through a screen and its mounting,

FIGURE 2 is a cross-section on the line 2-2 of FIG- URE l looking in the direction of the arrows,

lifliiil Patented Dec. 3, i963 ice FIGURE 3 is a plan with parts broken away to show the internal construction,

FGURE 4 is a vertical section through an apparatus containing several screens in series, and

FIGURE 5 is -a longitudinal section through an alternative form of screen.

A strong lateral frame is provided having longitudinals 11, 12 along the side which may, `for example, consist of stout angle iron. Between these there is disposed a `screen consisting of perforated or reticulated material for example wire gauze in two sections 13, 14 each of which is stretched between two parallel side-pieces of angle section metal 15, 16 for one section and `17, 18 for the other. The side-pieces are preferably in a light-weight alloy and they are drawn apart from one another by a number of tension springs 19 which connect them to the side lfrarne longitudinale 11, 12, of the machine. The screen material is each tset with a slight slope upwards to the left and in the centre the upper edge of the section 13 overlaps the lower edge of the section 14 with a small space between them. The angle members 15, 16 and 17, 18 are suspended on inclined laminated springs 20 constitute guide means for the screen as they extend from fixing blocks 22 secured below upper fixed longitudinals 21 above each side of the screen of the side frames and which are all arranged parallel to one another in an inclined direction: Thus as the screen sections vibrate upon the spring suspension members 26, they are guided by the springs 19 so as to move partly longitudinally and partly up and down. The two screens 13, 14 disposed between the side frames are vibrated in opposite phase by a mechanism which comprises a T-shaped -lever 23 at each side of the screens close to their junction. Each of the T-shaped levers Z3 is pivoted to pedestal bearings 24 at the crossing point of the T and the leg 25 of the T extends in an inclined direction upwardly and is reciprocated by a connecting rod 25 from eccentrics 27 on a motor driven. cross shaft 28 above the side frames of the machine. One arm oi the head of the T-shaped lever 23 extends upwardly from the pivot in a sloping direction and is connected by a link 29 to one of the spring supported angle members of the section 13 of the screen and the other arm of the head of the T-shaped lever Z3 extends downwardly and is connected by a similar link 39 extending in the opposite direction to the other section 1d of the screen. The two sections of the screen therefore vibrate in opposite phase and their inertia forces are balanced. `Each section is moreover extremely light owing to its construction and to the tension-spring supports 19. The speed of the vibration may be of the order of i() complete vibrations per minute or more.

In addition the space above the screen is covered over by a cove-raplate 32 and `in Athe centre of the covered portion above the screen there is a fan 33 mounted on a vertical axis and driven by skew-gearing in a gear box 34 `from the cross shaft 213 which carries the eccentrics. Below the coveppllate 32 -is a perforated plate 35 through which air `drawn up through the screen sections 13, 14 is conducted to the inlet of the fan. To this end the plate 5 is bent down beneath the fan 313 in the centre and a deilector plate 36 having a fan inlet 37 is lixed around and below the fan, below `the cover-plate 32. Around the fan above -deector plate 36 is an outlet into two lateral delivery ducts 38, 39 which deliver the air drawn up through the screen Iby the fan into side `delivery lchutes 4t?, 41 by which the air is conducted again to a space 42 below the screen and is thus circulated through any material on the screen. In being circulated the air may be caused to pass heating `or cooling devices `or both, so that moisture is either removed from the treated surface or is added to the material thereon as may be required for lthe purpose of bringing it into a desired condition. In the drawing, steam-circulation pipes 43 are indicated for this purpose. Material to be treated, for example tobacco, is delivered to the screen at one end and is propelled thereby through the machine, while the conditioning air ensures that not only is dust removed by the screen but all the materia-l treated is brought to the desired moisture content and state of aeration, which is .important in preparing tobacco vfor use.

When moisture has lto be removed, an auxiliary fan may be provided at one end of the apparatus which draws out a proportion of the air which is being circulated b-y the fan 313-. Therefore, on the average, every part of the air will circulate several times through the tobacco or the like being aerated and will then be withdrawn by the auxiliary fan.

In using the above-described apparatus the pairs of screens, vibrating in opposite phase, act as conveyors and if they are located high enough to be overhead they can be suspended from `the ceiling and will occupy virtually no floor space. Thus, material can be screened and conveyed simultaneously without displacing other apparatus.

Several conveyors each consisting of reticulated material held in stretched condition by lateral suspension springs in the manner `a'bove described, may be arranged -in a framework one above another, as shown in FIGURE 4, `being ydriven from -a motor by vi-bratory driving means similar to what has already been described, diiferent parts of the screens being arranged `to reciprocate in different phases so that the reciprocating forces are substantially balanced.

All the screens 50, 51, 52 FIGURE 4, are arranged to tend to propel the material toward the left-hand end of the framework as yviewed in FIGURE 4 and they are all enclosed in `a casing `S3. A=t the end towards which the material is propelled there are winnowers 54, 5S- each of which consists of a dr-um having around its periphery a number of radial lblades S6 which extend parallel with .the axis. The winnowers 4are surrounded on `their external sides by semi-circular parts of the casing and any material dropped on to the upper surface of a winnower is projected horizontally over the screen surface adjoining the winnower as indicated by the arrows 57, 58. The means for maintaining the conveyors of FIGURE 4 in laterally stretched condition are not shown in the drawing being identical with the corresponding means 15, 16 and 19 shown in FIGURE 2. It is to be understood that the anchoring means Z2 to which the suspension members 20 are attached in FIGURE 4 are xed in each case, the members 22 above the lower screens 51 and 52 being secured at their ends by appropriate means of attachment to framework of the apparatus which is not shown in the drawing, and hence held stationary. Assuming, for example, that material such as tobacco is being treated, the heavier and generally wetter stem portions are projected by the :winnower in a horiznotal direction above the screen surface with a greater momentum than the lighter portions. The heavy portions therefore, in proportion to their weight-surface ratio, get driven towards the back end of the screen as indicated by arrow 57 and the screen takes longer to propel them back towards the discharge end, while the lighter portions which are drier `and need less treatment have -to make only a shorter journey as indicated by arrow 53. Each screen delivers the material (which is distributed upon it by the winnower in accordance with its weight-surface ratio) toward the end which faces the winnower where it drops on to another winnower of the next stage below, and so on through the series. The result is that when 4the material comes out of the apparatus it has all been dried and aerated toy approximately the same extent notwithstanding the initial differences caused by the presence of stalks or clotted aggregates `in the tobacco.

As will be evident, different screens for sieving, heating, drying and cooling may be combined in this one machine.

In order to process material in which it is `desirable to maintain powder -that could drop through wire-mesh, each screen may be arranged in unperforated sections sloping gradually upwards and overlapping one another, so that the material is propelled up the sloping surface of each section and cascades from the upper edge down on to the next sloping section, and so on throughout the length of the screen, as shown by the slats 60 in FIGURE 5 which are supported on side member l5 similar to those shown in FIGURE 3 and carried by side springs (not shown in FIGURE 5) similar to the springs 19- of FIGURE 3, Air comes up between the slats, as shown by arrows 61.

Instead of circulating air upwardly through the screens or slats it is advantageous in certain cases to circulate it downwardly because this does not tend to carry away the lighter particles in the material to be treated. The exceptionally violent vibration which can be imparted to the material under treatment by the screens according to this invention tends to keep the material in a loose fluffy state even under a strong down draught of air.

Balancing of the reciprocating motor by a counterweight may be substituted for yba-lacning one part of the screen against another, if desired. Other materials which can advantageously be treated, apart from tobacco, are wool, cotton, tea, grain and chemicals, especially flaky, fibrous and granular materials. It will be noted that the apparatus of the present invention 4acts as a conveyor as well as a screen and the apparatus of FIGURE 5 may act principally or wholly as a conveyor and not as a screen so that the expression vibratory screens is to be read as having a broad meaning including conveyors.

I claim:

l. In a vibratory screen, the combination of a plurality of screening-surface elements which are arranged end to end in a substantially common plane, rigid side members atached to and extending along each side edge of each said element, spring means distributed along each of said side members in a substantially horizontal plane substantially parallel to the screening-surface elements to draw them apart and put the screening-surface elements in transverse tension, a frame to support the springmeans, driving-members attached to both said rigid side members of each screening element to reciprocate them longitudinally, link means inter-connecting the driving members so that the screening elements are caused to reciprocate in opposite phase and means to operate the link means at resonant frequency of the screen elements and spring-means.

2. A vibratory screen having the combination of claim l2 wherein the spring-means consist of tension springs each anchored at one end to the frame and at the other end to the said rigid side members so that they are free to rock at their anchoring points.

3. A screen as claimed in claim l wherein the frame is made in a box-construction so as to enclose the screens, with an outlet above the screens and an inlet below, and wherein fan means is mounted above the screen with the fan inlet xed therebelow to circulate air through the screen from the outlet back to the inlet.

4. A screen as claimed in claim l wherein the frame is made in a box-construction so as to enclose the screens, with an outlet from the part of the box which encloses one face of the screens and an inlet to the part enclosing the other face, and wherein fan means is mounted above the screen with the fan inlet xed therebelow to circulate air through the screen from the outlet back to the inlet.

5. A vibratory material treating apparatus comprising a fixed frame including a pair of side members arranged in parallel spaced relation to one another, a material treating surface element, stiff side-pieces attached to and extending along each side edge of said element inwardly of and spaced from said side members in substantially the same horizontal plane therewith, coil springs one end of each of which is anchored at intervals along the length of each side-piece, each of said springs having its other end anchored to said side member, said coil springs being disposed in a substantially horizontal plane and substantially parallel to the said material treating surface element so as to support the said element under transverse tension, the ends of said element being free, means for reciprocating the side-pieces together in the direction of their length, means including suspension members atached to the side-pieces and extending therefrom in an inclined direction relative to the plane of the treating surface of said element, fixed anchoring means located at the ends of said suspension members which are remote from the side pieces, the suspension members being engaged with the anchoring means for causing the sidepieces and the element to move together at an angle to said plane of the treating surface of said element.

6. A vibratory material treating apparatus as claimed in claim 5 further comprising a series of said elements and side-pieces arranged one above another and having delivery ends one above another, and a rotatable winnowing drum located adjacent the delivery end of the second element of said series of elements and each succeeding element of said series of elements and extending above and below the plane of its adjacent element, each of said drums also being located in the path of the material being treated as it is delivered from the preceding element of the series so that said material falls upon the winnowing dmm and said drum is rotated in a direction to fling said material upon the treating surface of the next succeeding element in a direction opposite to the direction of delivery of the material from said next element so that the heavier material being treated is thrown upon the treating surface of said next element at a further distance from the delivery end thereof than is the lighter material so that said heavier material will be subjected for a longer period of time to the treating action than is the lighter material.

7. A series of reciprocable conveyor screens arranged one above another, each comprising an elongated screening-surface element, stiff side members attached to and extending along each side edge of said element, coil springs each anchored at one end to each side member, the springs being spaced at intervals along the length of said side members in a substantially horizontal plane substantially parallel to the screening-surface element, a xed casing around the screens and springs to the interior of which the springs are anchored so as to support the screening-surfaces under transverse tension, suspension members attached to each side member and extending thererom at an inclination to the screening surface, fixed anchoring means located at the ends of the suspension members which are remote from the side members, the suspension members being attached to the anchoring means, so that when reciprocated the screens act to deliver material resting on them towards one end of each screen, means for reciprocating the side members and screens, and rotary winnowing drums below the delivery end of each screen except the last located in the path of material delivered by the screen so as to engage it and throw it back over the surface of the screen below the one from which it was received.

References Cited in the rile of this patent UNITED STATES PATENTS 33,956 Miller Dec, 17, 1861 302,570 La Rose July 29, 1884 525,758 Craney Sept. l1, 1894 997,016 Slaybaugh Iuly 4, 1911 1,728,657 Binte Sept. 17, 1929 1,983,676 Reynolds Dec. 11, 1934 2,661,812 Slater Nov. 24, 1936 2,402,341) Parmenter June 18, 1946 2,775,347 Weston Dec. 25, 1956 FOREIGN PATENTS 491,475 Great Britain Sept. 2, 1938 781,973 Great Britain Aug. 14, 1957 

1. IN A VIBRATORY SCREEN, THE COMBINATION OF A PLURALITY OF SCREENING-SURFACE ELEMENTS WHICH ARE ARRANGED END TO END IN A SUBSTANTIALLY COMMON PLANE, RIGID SIDE MEMBERS ATTACHED TO AND EXTENDING ALONG EACH SIDE EDGE OF EACH SAID ELEMENT, SPRING MEANS DISTRIBUTED ALONG EACH OF SAID SIDE MEMBERS IN A SUBSTANTIALLY HORIZONTAL PLANE SUBSTANTIALLY PARALLEL TO THE SCREENING-SURFACE ELEMENTS TO DRAW THEM APART AND PUT THE SCREENING-SURFACE ELEMENTS IN TRANSVERSE TENSION, A FRAME TO SUPPORT THE SPRINGMEANS, DRIVING-MEMBERS ATTACHED TO BOTH SAID RIGID SIDE MEMBERS OF EACH SCREENING ELEMENT TO RECIPROCATE THEM LONGITUDINALLY, LINK MEANS INTER-CONNECTING THE DRIVING MEMBERS SO THAT THE SCREENING ELEMENTS ARE CAUSED TO RECIPROCATE IN OPPOSITE PHASE AND MEANS TO OPERATE THE LINK MEANS AT RESONANT FREQUENCY OF THE SCREEN ELEMENTS AND SPRING-MEANS. 